go to the doc! don't let a treatment result in ostracism. medicine is supposed to improve your quality of life!
when I had trouble with GI symptoms it was from mag oxide and I switched to a more absorbable form. problem solved.
unfortunately I can't offer strategies to deal with tecfidera side effects, other than things to combat diarrhea, like zinc and iron
also potentially psyllium husk (aka Metamucil), which would help turn liquid into gel (not sure it would affect urgency though)
my approach: no meds so far - just nutrient-dense anti-inflammatory whole foods, and supplements where needed
info: www.whfoods.com, www.nutritiondata.com